1) Field of the Invention
The present invention relates to a technology for taking a back-up of data and also checking whether the data has been altered.
2) Description of the Related Art
The data, for example, original documents, needs assurance of authenticity at all times. Generally, a back-up of the data is taken to prevent loss of the data in case the hardware that stores the data fails. Moreover, by comparison of the original data and the backed-up data it is possible to check the authenticity of the data. The authenticity includes requirements such as data integrity, confidentiality, and readability, and the authenticity mentioned here indicates the data integrity.
Japanese Patent Application Laid Open No. 2003-022009 (pages 1 and 2, FIG. 1) discloses a related technology. According to the technology disclosed in this publication, access to the data is not allowed when the process of back-up or checking of the authenticity is being performed. However, according to this technology, because all the requests for the access to the data are denied, even the instructions for usual operations are also ignored. Moreover, because it takes much longer time for checking of the alteration of the data than for taking a back-up of the data, no other operation can be performed during when the checking of the alteration of the data.